In these years, as circuit patterns used in semiconductor devices are becoming finer, dimension accuracy in the lithography process is becoming one of especially important things. To date, various techniques to improve the dimension accuracy have been proposed. One of them is the method which adjusts the band width of laser light. Here, the depth of field (DOF) for patterns is expressed by DOF=(k2×λ)/NA2, where NA is the numerical aperture of the lens, λ is the light source wavelength, and k2 is a process factor.
As seen from this formula, the light source wavelength affects the magnitude of the depth of field. Hence, generally in the lithography process, laser light having a narrow band width close to being a single wavelength is used.
Meanwhile, the above formula can also be read as meaning that by changing the band width of the laser light, the contrast of a subject pattern can be changed. Hence, the band width of laser light may be used as a means of adjusting dimension differences between patterns due to an optical proximity effect.
However, by this method, on-substrate patterns having desired two-dimensional shapes cannot be formed with high accuracy. Hence, it is desired to form on-substrate patterns having desired two-dimensional shapes with high accuracy.